This invention relates to electronic circuits, and more particularly to an electronic circuit for controlling or regulating the speed of rotation of a microgenerator, of the type having a first input and a second input which can be connected to the microgenerator, an oscillator supplying a reference signal of a predetermined frequency, an energy-dissipation circuit for braking the microgenerator, energy-dissipation control means for controlling the energy dissipation of the energy-dissipation circuit as a function of the reference signal and of the signal between the mentioned inputs, a rectifier and voltage-multiplicating circuit for rectifying and multiplying the signal between the first and second inputs, the rectifier and voltage-multiplicating circuit containing at least one capacitor which can be charged by the microgenerator via at least one switch, and at least one control circuit of the mentioned switch or switches.
The invention further relates to a watch movement containing a circuit of the aforementioned type.
Numerous miniaturized electronic and electromechanical apparatus require an independent source of power. This source often consists of a battery pack or of solar cells. Batteries lead to various kinds of trouble, such as limited life, annoyingly frequent replacement, increased costs, and pollution of the environment. Solar cells operate only when there is sufficient light and require an additional store of energy. Further, their disposal may likewise lead to environmental problems, and fitting them into miniaturized apparatus such as watches, for instance, is difficult and leads to significant design restrictions.
In order to avoid such trouble, it has been proposed, e.g., in the U.S. Pat. No. 3,937,001, to replace the batteries of a watch movement by a generator and a spring driving the generator. The watch movement described contains a spring which, via gearing, drives a time display and a generator supplying an AC voltage. The generator feeds a rectifier, the rectifier feeds a capacitive component, and the capacitive component feeds an electronic reference circuit having a stable quartz oscillator and an electronic control circuit. The electronic control circuit has a comparator logic element and an energy-dissipation circuit connected to the output of the comparator logic element and controllable in its power draw by the comparator logic element. One input of the comparator logic element is connected to the electronic reference circuit and another input of the comparator logic element is connected to the generator. The comparator logic element is designed in such a way that it compares a clock signal coming from the electronic reference circuit with a clock signal coming from the generator, controls the magnitude of the power draw of the energy-dissipation circuit as a function of the result of this comparison, and in this way, via the control of the control-circuit power draw, controls the running of the generator and thus the running of the time display. In such a watch, the advantages of a mechanical watch, i.e., the absence of batteries, are combined with the accuracy of a quartz watch.
European Patent Application No. 0 239 820 and European Patent No. 679968 describe different electronic circuits for controlling the speed of a microgenerator in which a monitoring circuit constantly monitors the angular position of the rotor and brakes it as soon as its angular position is in advance. Because of their sensitivity to errors and phase variations of the components, these circuits are difficult to manage.
International Patent Application No. PCT/EP96/02791, the disclosure of which is incorporated in the present application by reference, describes an improved electronic control circuit which can be used in such a device. This application describes in particular a control circuit in which a voltage multiplicating circuit rectifies and multiplies the signal between the terminals of the generator. The voltage multiplicating circuit contains various capacitors C1, C2, C3 fed by the microgenerator through active elements, e.g., through field-effect transistors instead of diodes. Diodes are used only for initializing the system. In this way, the energy efficiency of the circuit can be greatly improved in that the threshold voltage losses of the diodes are avoided. Thus, the circuit can operate with a lower generator voltage, allowing a reduction in size of the generator and the spring and an increase in the power reserve of the watch movement. Furthermore, means are described for interrupting the braking of the microgenerator periodically so that optimum charging of the capacitors is ensured.